Polywell for spacecraft

[Quaoar]

Hi all,
I'm an italian dilectant SF writer. I was looking for realistic spacecraft for interplanetary travel in our solar sistem, and I found on-line Dr. Bussard's very interesting spacecraft based of fusor Polywell.

Dr. Bussard's engine, QED/ARC, QED/CSR and DFP, match very good with the plot of my novel, so I intend mount it on my fictional space ships, but I have two question for the experts of this forum. Can you help me please?

1) I found a lot of detail about QED/ARC, QED/CSR-A and DFP, but I founs very little information about a Dr Bussard's thruster called QED/CSR-B. On a paper on-line I read only that acceleration of propellant is not thermal, but is via a system called "collective acceleration in wave traveling beam".
How does it work exactly?
Is something like an electron beam driven plasma accelerator?
Wich are the limits of specific impusle of this kind of thruster?
Where can I find more information about it?

2) It is technically feasible (in the novel we are almost in 3000 BC) to use the relativistic electron beam (REB) of a QED rocket to drive also a free electron laser gun, something like a powerfull QED/FEL gun?

Thanks to all and sorry for my poor English

Quaoar

[Betruger]

This doesn't answer your questions, but I thought you might be interested, if you don't already know it.

[djolds1]

1) I found a lot of detail about QED/ARC, QED/CSR-A and DFP, but I founs very little information about a Dr Bussard's thruster called QED/CSR-B. On a paper on-line I read only that acceleration of propellant is not thermal, but is via a system called "collective acceleration in wave traveling beam".
How does it work exactly?
Is something like an electron beam driven plasma accelerator?
Wich are the limits of specific impusle of this kind of thruster?
Where can I find more information about it?

CSR-B looks like an MHD system. One of the papers at Askmar ("From SSTO to Saturn's Moons") cites thermal limits due to accelerator magnets. A chart in the same paper puts the Isp range for CSR drives between ~8000 to ~80,000 seconds, and thrust-to-weight between ~3 & .~03.

2) It is technically feasible (in the novel we are almost in 3000 BC) to use the relativistic electron beam (REB) of a QED rocket to drive also a free electron laser gun, something like a powerfull QED/FEL gun?

You probably could shove a polywell powered REB into the wiggler for a free electron laser. Given a scifi setting, there's no need to go into detailed explanation. OTOH, spare Gigawatts give you a lot of room to play with.

[Quaoar]

CSR-B looks like an MHD system. One of the papers at Askmar ("From SSTO to Saturn's Moons") cites thermal limits due to accelerator magnets. A chart in the same paper puts the Isp range for CSR drives between ~8000 to ~80,000 seconds, and thrust-to-weight between ~3 & .~03..

Thank you very much, I have found the article.
I'll probably use a double propulsione system with QED/ARC for orbital manouver and DFP for deep space interplanetary navigation. DFP need less radiator surface so I tink is moore pratical for warship.

You probably could shove a polywell powered REB into the wiggler for a free electron laser. Given a scifi setting, there's no need to go into detailed explanation. OTOH, spare Gigawatts give you a lot of room to play with.

I'm oriented on use a SASE single pass, to not have trouble with overheating the resonating cavity. Due to the not very high energy of the electrons (is a quasi-relativistic electron beam) probably the frequency range will be in the infrared region. Is correct?

best regard
Quaoar

[djolds1]

CSR-B looks like an MHD system. One of the papers at Askmar ("From SSTO to Saturn's Moons") cites thermal limits due to accelerator magnets. A chart in the same paper puts the Isp range for CSR drives between ~8000 to ~80,000 seconds, and thrust-to-weight between ~3 & .~03..

Thank you very much, I have found the article.
I'll probably use a double propulsion system with QED/ARC for orbital maneuver and DFP for deep space interplanetary navigation. DFP need less radiator surface so I think is more practical for warship.

Peruse the link Betruger provided, in depth, and salivate.

A realistic warship needs maneuver, not legs, and DFP is optimized for low accelerations and long range. A warship needs to quickly shift its aspect to minimize damage from beam weapons and long rod KE impactors. That requires high thrust. And radiators can be armored - use droplet radiators and all you need to worry about is the masts.

If you want high realism, a warship suitable for out to Neptune orbit should IMO be an ARC/CSR hybrid. Control beyond 30AU out with only QED rockets is pointless - the "nomads" would be too thinly spread in the Kuiper Belt.

You probably could shove a polywell powered REB into the wiggler for a free electron laser. Given a scifi setting, there's no need to go into detailed explanation. OTOH, spare Gigawatts give you a lot of room to play with.

I'm oriented on use a SASE single pass, to not have trouble with overheating the resonating cavity. Due to the not very high energy of the electrons (is a quasi-relativistic electron beam) probably the frequency range will be in the infrared region. Is correct?

I don't know. My advice would be to minimize the technobabble. Have the technology just work; bad sf spends waaaay too much time justifying how things function. Let the readers' imaginations fill in the details and you grab their attention much more effectively.

Duane

[IntLibber]

CSR-B looks like an MHD system. One of the papers at Askmar ("From SSTO to Saturn's Moons") cites thermal limits due to accelerator magnets. A chart in the same paper puts the Isp range for CSR drives between ~8000 to ~80,000 seconds, and thrust-to-weight between ~3 & .~03..

Thank you very much, I have found the article.
I'll probably use a double propulsion system with QED/ARC for orbital maneuver and DFP for deep space interplanetary navigation. DFP need less radiator surface so I think is more practical for warship.

Peruse the link Betruger provided, in depth, and salivate.

A realistic warship needs maneuver, not legs, and DFP is optimized for low accelerations and long range. A warship needs to quickly shift its aspect to minimize damage from beam weapons and long rod KE impactors. That requires high thrust. And radiators can be armored - use droplet radiators and all you need to worry about is the masts.

If you want high realism, a warship suitable for out to Neptune orbit should IMO be an ARC/CSR hybrid. Control beyond 30AU out with only QED rockets is pointless - the "nomads" would be too thinly spread in the Kuiper Belt.

Stephenson does a good job on such a ship design in his Anathem novel.

Pulsed fusion propulsion, a polygonal outer shield/shock absorption structure. Orion used shaped nuclear charges to direct thrust at the pusher plate. These would also be useful to direct the charges energies at attackers, or outright build specialized x-ray laser charges you shoot out of the vehicle, they shoot at your enemies while the blast provides thrust to move the vehicle away from the fight, leaving a hot plasma to muck up the enemy's ability to detect you.

FYI, "a ship suitable out to neptune orbit" is a misnomer. There is no such thing as range, there is only dV. A warship of course needs maximum dV during an engagement, when he can't maneuver anymore, he is most certainly dead.

It is a rule of space propulsion that any propulsion system sufficient to provide classical SF performance, requires very high specific impulse AND high thrust for sustained accelerations over 1 G for interplanetary and/or interstellar distances. Any such propulsion system is SO energetic that itself qualifies as a weapon of mass destruction (which is also obviously why no future government would let some juvinile twits go jousting about the verse in one, hence space pirates will not exist).

[djolds1]

Stephenson does a good job on such a ship design in his Anathem novel.

Pulsed fusion propulsion, a polygonal outer shield/shock absorption structure. Orion used shaped nuclear charges to direct thrust at the pusher plate. These would also be useful to direct the charges energies at attackers, or outright build specialized x-ray laser charges you shoot out of the vehicle, they shoot at your enemies while the blast provides thrust to move the vehicle away from the fight, leaving a hot plasma to muck up the enemy's ability to detect you.

Niven/Pournelle captured the concept well with their "Michael" battleship in Footfall, and Stirling did as well in The Stone Dogs.

FYI, "a ship suitable out to neptune orbit" is a misnomer. There is no such thing as range, there is only dV. A warship of course needs maximum dV during an engagement, when he can't maneuver anymore, he is most certainly dead.

True. But even the better "near term" notional design studies (EPPP/nuclear pulse, Nuclear Salt Water Rocket, Bussard QED) limit themselves to ~ 100,000m/s dv. If you want relatively rapid transit, that does impose "range" limits. Also, there are politics. Beyond the planetary subsystems and major asteroid belts (Main, Greek, Trojan) there's not much worth controlling.

It is a rule of space propulsion that any propulsion system sufficient to provide classical SF performance, requires very high specific impulse AND high thrust for sustained accelerations over 1 G for interplanetary and/or interstellar distances. Any such propulsion system is SO energetic that itself qualifies as a weapon of mass destruction (which is also obviously why no future government would let some juvenile twits go jousting about the verse in one, hence space pirates will not exist).

You don't need 1G+ for long, just for combat maneuvering and climbing out of deep gravity wells. Low accel is sufficient for all other times. It seems to me that an ARC/CSR hybrid is good for both regimes.

1G or greater for a week+ and you're into relativistic impactor territory.

[D Tibbets]

... politics. Beyond the planetary subsystems and major asteroid belts (Main, Greek, Trojan) there's not much worth controlling.

Not much there? From Wikipedia -
"Since the first discovery in 1992, the number of known Kuiper belt objects (KBOs) has increased to over a thousand, and more than 70 000 KBOs over 100 km in diameter are believed to reside there".

Several are in the Pluto size area and led to the IAU redefining planets ( a faulty and silly nomenclature).

And, then there is the Ort Cloud...

Dan Tibbets

[krenshala]

... politics. Beyond the planetary subsystems and major asteroid belts (Main, Greek, Trojan) there's not much worth controlling.

Not much there? From Wikipedia -
"Since the first discovery in 1992, the number of known Kuiper belt objects (KBOs) has increased to over a thousand, and more than 70 000 KBOs over 100 km in diameter are believed to reside there".

Several are in the Pluto size area and led to the IAU redefining planets ( a faulty and silly nomenclature).

And, then there is the Ort Cloud...

Dan Tibbets

Then there is the fact that if there is something useful, whatever it may happen to be, then someone will find the area worth controlling. Now, whether they can actually control it is a different matter.

[KitemanSA]

Several are in the Pluto size area and led to the IAU redefining planets ( a faulty and silly nomenclature).

True. By the new definition, there was a time about 4 billion years ago when Earth, (about the size it is now and bigger than the planet Mars) was a "dwarf planet". Then all the sudden, less than an hour later, shazaam, its a planet! Silly indeed.

What happened you ask? In that time frame, a roughly Mars size chunk of rock collided with Earth and became small enough pieces to not count. You see, BEFORE the collision, Earth had not cleared its neighborhood, while after it, it had. And that is the distinction they are trying to foist off on us poor unsuspecting users of the language.

It should also be noted that Earth had more orbits before the collision, more orbits to clear that last major hunk, than Pluto has had since the beginning of the Solar System to clear it's neighborhood, and Pluto's is a MUCH bigger neighborhood!

[D Tibbets]

The part about clearing ones orbit is indeed the silly part. Certainly the Earth cleared out the Mars sized world billion of years ago, with the Moon being the result of some of the splattered debri. And, Earth has had many large impacts since. Curently it is estimated that there ~ 10,000 Earth crossing asteroids that are large enough to detect. Earth has not cleared out its orbit yet, so it is not a planet by the current definition.
Wait, if you claim that these are perterbed asteroid orbits (new) then it's just that the Earth hasn't yet had time to clear them. But, if you use this argument, you have to accept that the definition only applies in a stable system, which the solar system will never be. A grain of dust has cleared it's orbit, at least untill it meets something bigger. Any definition would be arbitrary, but at least you don't need to include a transiant condition like this.


Dan Tibbets

[djolds1]

... politics. Beyond the planetary subsystems and major asteroid belts (Main, Greek, Trojan) there's not much worth controlling.

Not much there? From Wikipedia -
"Since the first discovery in 1992, the number of known Kuiper belt objects (KBOs) has increased to over a thousand, and more than 70 000 KBOs over 100 km in diameter are believed to reside there".

Several are in the Pluto size area and led to the IAU redefining planets ( a faulty and silly nomenclature).

And, then there is the Ort Cloud...

Very dispersed, and very distant. The planetary subsystems and primary asteroid belts (Main, Greek, Trojan) are the most favorable sites for resource acquisition, eventual dense settlement, and the military control that settlement will in time require. IMO "military spacecraft" in any hard scifi scenario in the near to mid future should have drives optimized to those high density regions. And Bussard ARC/CSR hybrids fit the bill. "Pirates and Nomads" can float around in their KBO habitats, but they don't matter until they annoy the Empire with raids on the core regions.

Bring in "reactionless" drives and/or FTL however, and any "standard" delta-v figures for "Solar System Empires" go out the window.

[IntLibber]

... politics. Beyond the planetary subsystems and major asteroid belts (Main, Greek, Trojan) there's not much worth controlling.

Not much there? From Wikipedia -
"Since the first discovery in 1992, the number of known Kuiper belt objects (KBOs) has increased to over a thousand, and more than 70 000 KBOs over 100 km in diameter are believed to reside there".

Several are in the Pluto size area and led to the IAU redefining planets ( a faulty and silly nomenclature).

And, then there is the Ort Cloud...

Very dispersed, and very distant. The planetary subsystems and primary asteroid belts (Main, Greek, Trojan) are the most favorable sites for resource acquisition, eventual dense settlement, and the military control that settlement will in time require. IMO "military spacecraft" in any hard scifi scenario in the near to mid future should have drives optimized to those high density regions. And Bussard ARC/CSR hybrids fit the bill. "Pirates and Nomads" can float around in their KBO habitats, but they don't matter until they annoy the Empire with raids on the core regions.

Bring in "reactionless" drives and/or FTL however, and any "standard" delta-v figures for "Solar System Empires" go out the window.

Useful transit distances depend on whether practical medical suspension techniques can be perfected that do not cause brain damage but do significantly slow metabolic processes and aging.

[hanelyp]

Useful transit distances depend on whether practical medical suspension techniques can be perfected that do not cause brain damage but do significantly slow metabolic processes and aging.

As far as I'm concerned it's not a question of whether such 'hibernation' tech is possible, but how soon, and how much it extends permissible transit time. There have been some intriguing animal studies using hydrogen sulfide. It appears that there are mechanisms built into animal metabolism to enter a reversible shutdown state in an oxygen free environment. The trick is triggering those mechanisms in a controlled fashion.

[Quaoar]

Very dispersed, and very distant. The planetary subsystems and primary asteroid belts (Main, Greek, Trojan) are the most favorable sites for resource acquisition, eventual dense settlement, and the military control that settlement will in time require. IMO "military spacecraft" in any hard scifi scenario in the near to mid future should have drives optimized to those high density regions. And Bussard ARC/CSR hybrids fit the bill. "Pirates and Nomads" can float around in their KBO habitats, but they don't matter until they annoy the Empire with raids on the core regions.

Bring in "reactionless" drives and/or FTL however, and any "standard" delta-v figures for "Solar System Empires" go out the window.

Thanks to all,
I'm oriented in use an ARC/CSR Hybrid equipped with very light weight furling ballistic conduction graphene radiators, propelled by a gel of liquid molecular Hydrogen.
In ARC mode, the radiators are furled in armoured compartiments and the rocket has exaust velocity from 15 to 110 km/s with high thrust.
In CSR mode the radiators are unfurled like the jib of the sailboats and the rocket can reach an exaust velocity up to 400-500 km/s (I think it is possible with an open frame design for the magnetic chamber and nozzle, where the west heat is directily irradiated in the space). In this modality, used in interplanetary transfert, the thrust is low, but the ship can have a complessive delta-V of 440-550 with a mass ratio of 3.

Best regard to all
Quaoar



uring the fighting and the orbital manuvering, the